Microfiltration and ultrafiltration equipment is required for many applications including the concentration; fractionation and ultrapurification of protein solutions; the depyrogenation of water and intravenous solutions; the desalting of biologicals; and the removal of macromolecules and colloids. A well-known type of such apparatus employs a filtration cassette comprising a stacked array of ultrafiltration membranes separated by flow accommodating screens and retained between demountable plates. Some of the problems associated with such equipment stem from the requirements for frequent cleaning and replacement of filtration cassettes. One ultrafiltration unit, for example, utilizes fluid flow parts in each of the demountable plates thereby necessitating dismantling of an entire system for each cleaning or filtration cassette replacement procedure. Other ultrafiltration units require specially designed filtration cassettes and are not compatible for use with commonly available filtration cassettes. One such unit is disclosed in U.S. Pat. No. 4,430,218. Another unit is disclosed in U.S. Pat. No. 4,715,955, which includes a housing having internal flow passages. The flow passages, however, are oriented to be perpendicular or parallel to the transverse edges of the housing which thereby provides horizontally-oriented surfaces on which leftover filtrate or feed/retentate fluid may collect from use of the housing. These horizontal surfaces therefore provide the potential for contamination when the housing is used in successive filtration operations.
There is therefore a need for a tangential filtration housing which reduces the risk of contamination of successive uses of the housing.